Power-operated hydraulic pressure device, including yieldable piston stop



May 27, 1952 E. .1. RINGER 2,598,604

' POWER-OPERATED HYDRAULIC PRESSURE DEVICE, INCLUDING YIELDABLE PISTONSTOP Filed Oct. 8. 1945 l I 1 ay v V U l 6? 40 3a z l 82 l :Fl 5.. Z

INVENTOR. fz aidfl/v ffi BY Patented May 27, 1952 POWER- PE AT D YD AUC, B t URE VICE, INCLUDING" YmLnnnnl p sgron Evue J. Ringer, South Bend,Ind., assignor to Bendix Aviation Corporation, South a"cexplorationofDelaware I show 1945, se al ia-fil fioi 8 class. (01.60 516) 1 onrelates to a power operincluding yieldable piston fishy to" the device3533755, h H presentinvention is v a unit o; the type'disclosed in saidpatent which will be an improvement thereover 1) in reducing the cost ofmaking the unit, and (2) in inciieafsingfthe reliability of operationof. the unit" to pr ovid "A-iiibi-' spefiific object of the presentinvention is to proyide in proyed means rerretraetmg the "e' p weroperatdnydra ine cylinder, ociated' therewith" for n sage; through said'piston is co rolled tan times; an is'sumeiently "the unit'i's inreleased posiflow or fluid therethro'ugh, turing tolerances. jec'tsa n'dadyantaes' of the present pastels: during the course i on} whereinreference'is a ny g'drawinain whit-hr lEigi'rre lis a eftlcal crosssectional View taken tie ioii'vgliitbli iiicoi'poratesmy'invem d'e ice,being the" combination of a 2 is an enlarged cross-sectional viewshwifi'g the rear'portitnbi the hydraulic cylinden oi Figure 1.

"Fl a cross section taken through the 'p 1ston treaties 1 and '2at'iight mas euse s own-n Figures 1 "and 2. U "a' d'ifii'ntial aifpressure V -t'l2'is arranged to V Tplstbn-iiia hydraulic actuator :4, 1ywitri'tna'assistah ce"of pressure we: niiefiti'onal manually operatedThe 'liydra'ulic actuator is disdain-eat or the invention is intendedld'vacuutn" the sourc'of power,

it it is constructed as a vacuumv the? thana n atmosphresuspefidedTherefore, thecoostafifipressure chamber h ift 't se ers? w re 2 2 isconnected by suitable means (not, shown) to avacuum source, such as theusual intake mani fold of an automotive vehicle; Control chamber isconnctewby means. of. conduit 24 with chamber 26' of. a control valve.28, which regulates operation ofthe-power cylinder, v

Pow'erpiston' [61 is biased to retracted position by. means'of a,relativelyfheavy return spring 3 whichis compressed between the forwardend 32 ofthe power cylinder and, the piston I-Ei The released orrtracted'p'osition of the power; piston is determined by contact thereoiwith the rear wall t l of the poWercylinder casing, a project'ion316'preferab1y being provided-at the rear of piston 16. adapted tocontactthe rear wall of the;

' power cylinder casing for this-purpose.

Reciproe'abl in hydraulic Y cylinder i4 is a piston 33, whi'ch dividessaid cylinder into arear chamber 40. and a forward chamber 52. Whenpiston 38 isin released position, as shown, cornmunicati'on betweenchambers 4 0 and is permitted by a passage 4.4, which extends longitudknally through the center. of said piston. An inlet opening 46 isintended to permit communication of "chamber 40 "with the conventionalmanually operable master cylinder, suitable conduitmeans being provided.An outlet'opening 4 8 is arranged to permit communication ofchamber 4 2,through suitable conduit means; with the motor ormotors which are to beoperated, such the conventiohalwheel cylinders of a hydllaullo brakesystem.

A pressure transmitting rod 50 is secured to power piston IS and extendsthrough an opening 52 in the forward end'of the power cylinder into thebore'of hydraulic cylinder [4; The forward end or rod 55 is secured'tohydraulic piston 38 by ns of a p itive c nn c ion, such as h .105 pinas. "There should be a sli ht l arance etween the pin'and the pin slotinorder that the end of the rod can act directly; against the hardenedthrust plate 57., which is pressed into piston 38. With this'arrangement," the power piston it controls both-the pressure stroke' andthe retraction strolseoi hydraulic piston'38 and the single returnspring 3,lI-ser ves the dual function of retracting both the powerpiston and the d aulic biston; Here Qfore it h sbeen 9 nsider ednecessary to provide separate return springs for the power andhydraulicpistons", but

' the pfesentinvention makes it possible to utilize a single-51 111181 9return be h fstons. 7

"When th ombina ion p w r, and dr u ic one another, in order thatchamber 42 and the wheel cylinders may compensate for variations in thevolume of the fluid by communication with the manually operated mastercylinder, which in turn is adapted to compensate for volume variationsin the fluid because of its direct connection with the usual integralreservoir. On the other hand, during the pressure stroke of hydraulicpiston 38 it is necessary that communication between chambers 40 and 42be prevented, otherwise the entire force developed by the power cylinderwill react against the manually operated master cylinder, and the fullbrake applying pressure will have to be developed by the operator.

In order to control the flow of fluid through passage 44, a valveelement 56 is provided. When the valve element 56 seats at 58, flow offluid from chamber 42 to chamber 40 is prevented, although flow in thereverse direction can still occur. A light spring 60, mounted in'aretaining case or cage member, 62, urges the valve element 56 to wardseated position.

Means must be provided to hold valve element '56 away from its seat whenpiston 38 is in released position. This means may take the form of thevalve unseating element 64 which has a forward projection 66 extendingthrough passage 44 to contact valve element 56, and which has offsetrearwardly extending projections 68 which are located in slot 16provided in piston 38 and which are adapted to contact a stop memberslightly before piston 38 has returned to released position, in orderthat said stop member will cause relative movement between member 64 andpiston 38 to force valve element 56 from its seat. Member 64 is looselyassembled in piston 38 by means of a snap ring 12 which is fixed inplace on the piston, and which extends into an elongated groove 14 ineach rear extension 68 of member 64. Snap ring 12 also serves to retainthe loose cross pin 54 in position.

Because of the accumulated tolerances in the power cylinder andhydraulic cylinder, it is impossible to have more than one definite stopfor the power and hydraulic piston combination to determine the releasedposition of said pistons. In arrangements of the type heretoforeprovided, in which the power piston and hydraulic piston were notpositively connected, it was possible to provide a separate stop foreach of them, and it was of course necessary to provide a separatespring urging each piston toward the respective stop.

When the power and hydraulic pistons are positively connected, as in thepresent case, if separate fixed stops are provided for each of saidpistons, then the presence of tolerances in the combination unit meansthat it is almost certain that one of the pistons will reach itsreleased position ahead of the other, and that the latter will thereforebe held away from fully retracted position. Such a situation has certainvery troublesome disadvantages. For example, if the hydraulic pistonreaches its retracted position ahead of the power piston, then theentire force of the large return spring 30 will have to be taken asa'shear load'on the small connecting pin 54. On the other hand, if thepower piston returns to its released position ahead of the hydraulicpiston, there is no guarantee that said hydraulic piston will have movedsufliciently far toward its released position to insure unseating ofball valve 56 by member 64. If the ball valve is not held away from itsseat when the parts are in released position, there is the danger that avaria tion in volume of fluid in chamber 42 of the wheel cylinder willcause the brakes to lock.

To obtain the advantages of a direct connection between the power pistonand the hydraulic piston, and at thesame time entirely overcome thedifliculty heretofore discussed, I have provided novel means for causingmember 64 to unseat valve element 56, regardless of the exact positionwhich piston 38 assumes when fully retracted. This means is a yieldablestop member arranged to contact valve unseating element 64 to cause apredetermined amount of relative movement between said member 64 andpiston 38, while yet limiting the shear load on pin 54 to a relativelylow amount. For this purpose, I provide a compression spring 16 locatedin the rear of chamber 40 and'compressed between the closure member 78and a washer or stop element 50. The washer '60 is prevented from movingtoward the right by means of a movement limiting member 82 which snappedinto a groove 84 provided in the inner wall of the hydraulic cylinder. Iprefer to use a non-circular resilient member for this purpose, such asa member having a hexagonal or octagonal shape, in order to avoid anydanger that the washer 80 might slip through the limiting member 82.

The spring I6 must be sufiiciently strong to overcome the force ofspring 60 plus any pressure differential in the hydraulic system tendingto hold valve 56 seated.

When the rearwardly extending forks of member 64 contact washer 80,further rearward movement of member 64 is prevented, and subsequentmovement of piston 38 towards the left will cause the valve seat 5 8 tomove away from valve element 56, thereby opening communication betweenchambers 40 and 42. However, if the rear surface, of piston 36 contactswasher before projection 36 of power piston l6 has engaged the rear wallof the power cylinder casing, spring 16, which is much lighter thanspring 30, will compress, permitting the hydraulic piston assembly tocontinue moving toward the left until the power piston has come to itsresting position. The full shearing load on pin 54 is therefore theforce exerted by spring 16, rather than that exerted by spring 30. Also,loads on the other ports of the hydraulic piston are limited to theforce of spring 16.

In making the combined power unit and hydraulic actuator, the tolerancesshould be so arranged that hydraulic piston 38 will never remain too farto the right when the power piston has reached fully retracted position.In other words, any tolerances allowed should be in the direction ofcausing compression of spring 16, thereby insuring that the returnmovement of piston 38 will always be suflicient to cause valve element56 to be moved away from its seat.

The general operation of the device is as follows. When the operatorwishes to apply the brakes, he develops pressure in the manuallyoperated master cylinder by means of the usual pedal. The fluid underpressure moves from the manually operated master cylinder through theconnecting conduits and through opening 46 into chamber 40. Because, inthe released position of the unit, valve element 56 is away from itsseat, a certain amount of the fluid may flow through passage 44 intochamber 42 and thence to the wheel cylinders to initiate application ofthe brakes. At the same time fluid under pressure from the manuallyoperated master cylinder moves from chamber '40 through passage 86 intochamber 88; to, act on piston x9 9, driving the, same,

cation. between chamber. 26 and chamber 9 6,

which, is. connected. to. vacuum. Further move.- ment of. pistonell. andvalveseat 9.2 pushes thrust connection 58 tO.-mV.e. valve element lflilaway from valve. seat [02,. thereby admitting air atatmosphericpressurefrom chamber N34 to chamber 25, whence. the air. is. conducted tocontrol chamber. 23}. of. the power cylinder, developing a pressure.differential. over power piston 16 which moves. thesame, towards theright against the resistance of return spring 33'. The force developedby thepower piston acts through rod 50 to driveipiston- 38' toward theright, the force being. exerted: directly against thrustplate '51.Sincemember 64 is only loosely assembled in piston 38., a slightmovement of said piston toward. the right. will. permit spring 60 tomove ball valve element 56 to seated position, after: which fluid. inhigh pressure chamber 42 can no longer. flow into. chamber 40, althoughit isstill possible for fluid. to flow in the reverse direction in.case. of power. failureor power run-out. The manually developedpressurewhich,is transmitted from the operator operated master cylinderto chamber 40 continues to assist in applying the brakes by exerting. apressure against the rear of piston 38.. Therefore, the work output atthe brake. is a total. of. the. work done by the power cylinder and.the. work done by the operator.

When the operator wishes to release the brakes, he releases. pressure inthe manually operated master cylinder. This reduces the pressure inchamber 49, and, also in chamber 88, permitting valve return spring. [B6to move member 92 toward the left, first causing valve element I00 toseat under the influence of spring I08, and subsequently causing valveseat 92 to move away from valve. element 94., again evacuating controlchamber 2001 the. power cylinder, and destroying the differential. overpower piston l6. This permits return spring 30. to force power piston I6toward the left, drawing with it hydraulic piston 33'. Just before thepower and hydraulic pistons have reached released position, member 64contacts washer 80 and forces ball valve element 56 away from its seat.As explained above, should it be necessary for piston 38 to move fartherto the left, after it has contacted washer 80, this is permitted byspring 16.

With the present arrangement, no initial adjustment is necessary tocompensate for manufacturing tolerances, because the proper control ofthe passage through the hydraulic piston is insured. Furthermore, largeparts of the unit, such as the power cylinder parts, can be bottomed orrested against a rugged structural element, i. e., the power cylindercasing.

Although a particular embodiment-of my invention has been described, itwill be understood by those skilled in the art that the object of theinvention may be attained by the use of constructions different incertain respects from that disclosed without departing from theunderlying principles of the invention. I therefore desire by thefollowing claims to include within the. scope of my invention all suchvariations and modifications by which substantially the results of myinvention may be obtained through the use of substantially the same orequivalent means.

I claim:

1. A combined differential air pressure powerunit and hydraulic actuatoroperated thereby 6 compri'sing a casing for the power unit; ap owerpistons reciprocable. therein, a hydraulic cylinder secured to the powercylinder casing and having.

a bore concentric with the. power; cylinder piston,

' a hydraulic piston reciprocable in said. bore, said hydrauliccylinder. having an inlet opening behind; Said; piston and; an outletopening ahead of said piston, said piston having a passage extending,longitudinally. through the center thereof constituting the, only meansof direct communication between the inlet and outlet openings, a valveelement at the forward end of said. passage which. when seated permitsnow of fluid only fromrthe inlet side toward the outlet side and not in,the reverse direction, a spring urging said. valve; element towardseated position, a rod secured, tothe. power cylinder piston andextending, into. the hydraulic bore to contact the hydraul'icpistomacross-pinproviding a lost motion return connection between the forwardendof the rod and; the hydraulic, piston, a relatively heavy springinthepowerunit acting against the power piston to. retract, both thepower piston and the hydraulic pistomsai'dpower piston having arearwardly extendin projection which contacts the powerunit casing whenthe piston is in retracted position,a, washer in thehydraulic cylinderwhich is; contacted by the rear oi the. hydraulic piston when. the.latter is in retracted position, a spring compressed, between theforward end of the power unit; casing and said washer to. opposeyieldably further return; movement. of the hydraulic piston after saidpiston has come into contact with the washer, said spring. beingsufficiently strong to overcome the, spring which urges the valveelement to seated. position plus any hydraulic pressure. acting on saidvalve element, but being relativelyweak in comparisonv to the springwhich returns the power piston. to released position, a movement.limiting member secured in a groove in the hydraulic cylinder andarranged to limit forward movement of the washer under the influenceofthe spring acting thereon, and a valve unseating member carried by saidpiston but capable of movement relative thereto and arranged to contactthe washer on the return stroke before the piston contacts said washer,thereby forcing the valve element from its seat to permit compensationfor changes in the volume of the liquidv on the. forward side ofthehydraulic piston.

2,. A combined differential air pressure power unit and hydraulicactuator operated thereby comprising a casing for the power unit, apressure responsive movable wall reciprocable therein, a hydrauliccylinder supported on the power cylinder casingand having a boreconcentric with the power cylinder movable wall, a hydraulic pistonreciprocable in said bore, said hydraulic cylinder having an inletopening behind said piston and an outlet. opening ahead of said piston,said piston having a passage extending longitudinally through the centerthereof constituting the only means of direct communication between theinlet and outlet openings, a valve element associated with said passagewhich when seated permits flow of fluid only from the inlet side towardthe outlet side and not in the reverse direetion, a spring urging saidvalve element toward seated position, a rod secured to the powercylinder movable wall and extending into the hyd eulic bore to est en th a lic i i qn 16stme ee e u n. conn c i n. b wee h -f end. of th r d.an th h drauli is n; a atively heavy spring in the power unit actingmember in the hydraulic cylinder which is contacted by the rear of thehydraulic piston when the latter is in retracted position, a springcompressed between the forward end of the power unit casing and saidstop member to oppose yieldably further return movement of the hydraulicpiston after said piston has come into contact with the stop member,said spring being sufficiently strong to overcome the'spring which urgesthe valve element to seated position plus any hydraulic pressure actingon said valve element, but being relatively weak in comparison to thespring which returns the movable wall to released position, a movementlimiting member secured inside the hydraulic cylinder and arranged tolimit forward movement of the stop member under the influence of thespring acting thereon, and a valve unseating member carried by saidpiston but capable of movement relative thereto and arranged to contactthe stop member on the return stroke before the piston contacts saidstop member, thereby forcing the valve element from its seat.

3. A combined difierential air pressure power unit and hydraulicactuator operated thereby comprising a casing for the power unit, apressure responsive movable wall reciprocable therein, a hydrauliccylinder having a bore concentric with the power cylinder movable wall,a hydraulic piston reciprocable in said bore, said hydraulic cylinderhaving an inlet opening behind said piston and an outlet opening aheadof said piston, said piston having a passage therethrough constitutingthe only means of direct communication between the inlet and outletopenings, a valve element associated with said passage which when seatedpermits flow of fluid only from the inlet side toward the outlet sideand not in the reverse direction, aspring urging said valve elementtoward seated position, a, thrust transmitting member secured to thepower cylinder movable wall and extending into the hydraulic bore to acton the hydraulic piston, a lost-motion return connection between thethrust transmitting member and the hydraulic piston, a relatively heavyspring in the power unit acting against the movable wall to retract bothsaid movable wall and the hydraulic piston, the released position ofsaid movable wall being determined by the power unit casing, a floatingstop member in the hydraulic cylinder which is contacted by the rear ofthe hydraulic piston when the latter is in retracted position, a springcompressed between the rear .wall of the hydraulic bore'and said stopmember to oppose yieldably further return movement of the hydraulicpiston after said piston has come into cotnact with the stop member,said spring being sufliciently strong to overcome the spring which urgesthe valve element to seated position plus any hydraulic pressure actingon said valve element, but being relatively weak in comparison to thespring which returns the movable wall to released position, a movementlimiting member secured inside the hydraulic cylinder and arranged tolimit forward movement of the stop member under the influence of thespring acting thereon, and a valve unseating member carried by saidpiston but capable of movement relative thereto and arranged to contactthe stop member on the return stroke before 8 the piston contacts said.stop member, thereby forcing the valve element from its seat.

4. In a power-operated hydraulic cylinder, a piston in the cylinderdividing it into two chambers, a conduit adapted to connect saidchambers, a valve controlling said conduit, a

resilient member urging said valve to close said conduit, a floatingmember associated with said valve capable of displacing the same to openthe conduit, a stop member which is engaged first by the floating memberand then by the piston when the latter approaches retracted position,and a spring which acts on said stop member to urge it toward the pistonand which is yieldable to permit movement of the piston and stop memberas a unit to reach fully retracted position.

5. In a power-operated hydraulic cylinder, a piston in the cylinderdividing it into two chambers, a conduit adapted to connect saidchambers, a valve controlling said conduit, a floating member associatedwith said valve capable of displacing the same to open the conduit, astop member which is engaged first by the floating member and then bythe piston when the latter approaches retracted position, and a springwhich acts on said stop member .to urge it toward the piston and whichis yieldable to permit movement of the piston and stop member as a .unitto reach fully retracted position.

6. A combined power unit and hydraulic actuator operated therebycomprising a casing for the power unit, a pressure responsive movablewall reciprocable therein, a hydraulic cylinder associated with thepower unit, a piston in the cylinder dividing it into two chambers, amechanical connection between the movable wall and the piston, a returnspring acting on the movable wall to return it and the piston toretracted position, a conduit adapted to connect the two chambers of thecylinder, a valve arranged to control said conduit, a member associatedwith said valve capable of. displacing the same to open the conduit, anda, yieldable stop which first causes the aforesaid member to move thevalve away from closed position as the piston returns to retractedposition and thereafter yields to permit further retractile movement ofsaid piston. I

7. A combined power unit and hydraulic actuator operated therebycomprising a casing for the power unit, a pressure responsive movablewall reciprocable therein, a hydraulic cylinder associated with thepower unit, a piston in the cylinder dividing it into two chambers, amechanical connection between the movable wall and the piston, a returnspring acting on the movable wall to return it and the piston toretracted position, a conduit adapted to connect the two chambers of thecylinder, a valve arranged'to control said conduit, a member associatedwith said valve capable of displacing the same to open the conduit, anda yieldable stop which causes the aforesaid member to move the valveaway from closed position as the piston returns to retracted position. 7

8. A combined power unit and hydraulic actuator operated therebycomprising a casin for the power unit, a pressure responsive'movablewall reciprocable therein, a hydraulic cylinder associated with thepower unit, a piston in the cylinder dividing it into two chambers, amechanical connection between the movable wall and the piston, a returnspring acting on the movable wall to return it and the piston toretracted position, a rigid stop which determines 9 10 the retractedposition of the movable wall, a REFERENCES CITED conduit adapted toconnect the two chambers of The following references are of record inthe the cylinder, a valve arranged to control said me of thi I atent.conduit, a member associated with said valve S p capable of displacingthe same to open the con- 5 duit, a stop member which is engaged by theUNITED STATES PATENTS piston when the latter approaches retracted po-Number Name Date sition, and a spring which acts on said step mem-2,246,140 Main June 17, 1941 her to urge it toward the piston and whichis ,2 0, 90 Stelzer Oct. 28, 1941 yieldable to permit movement of thepiston and 10 85 Elliott Dec. 14, 1948 stop member as a unit to reachfully retracted position.

EVUE J. RINIGER.

